Blackham Resources Ltd’s (ASX:BLK) tests have confirmed that transitional ores from the Matilda-Wiluna Gold Project can be processed through the existing CIL plant at a lower cost and improved recovery rate.
There is a substantial amount of free milling oxide and transitional ores above the top of fresh rock at open pits over the 4 kilometres of strike at Wiluna, which is in Western Australia.
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It was originally assumed in the August 2017 Wiluna expansion pre-feasibility study that this would be processed through the existing sulphide circuit.
However, new test work has demonstrated that the transitional ore gains higher recoveries through the operating CIL plant.
Cost about 30% less
It has also revealed that the processing cost is about 30% less than utilising the sulphide circuit.
Average leach recoveries on the oxide ores were 90.8% after 24 hours with little increase in recovery after that while recoveries on the transitional ores were 84.3%.
The brown and green oxide and transitional only pit optimisations in historical open pits
show the potential for free milling ore.
The test work on Wiluna oxide and transitional ores was carried out by Independent Metallurgical Operations Pty Ltd under the supervision of Blackham.
Follow-up drilling has been completed to obtain additional transitional ore samples for the next round of metallurgical test work.
Drilling results soon
During March 2018 Blackham drilled 84 reverse circulation holes for 6,491 metres focused on delineating further free milling open pit reserves and initial results are expected shortly.
This program followed up on 77,000 metres of drilling completed in 2017 which delivered probable reserves of 669,000 ounces of gold and included oxide, transitional and fresh reserves.
All of the historical open pits at the mine were processed through the CIL plant with the exception of the 2007 East pit cut back.
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Blackham is re-estimating the open pit free milling resources and reserves around the Wiluna mine site.
Management believes the free milling ores within the existing Wiluna mine footprint are an attractive feedstock for the operating mill and allows for fast-tracking mining approvals.